VANCOUVER -- Police appear to be cracking down on pop-up stalls selling marijuana while frustrations mount over the open-air market operating in a prominent square in downtown Vancouver.

A spokesman for the Vancouver Police Department declined comment on what he called an ongoing investigation, but vendors said Monday that officers raided merchants' tables in Robson Square the night before and arrested several sellers.

Pop-up pot stalls began appearing on a monthly basis about two years ago in the pedestrian-only plaza, but vendors have been setting up with increasing frequency in recent weeks, selling everything from dried marijuana to cannabis-infused edibles.

Ron Woodruff said he was thrown to the ground by police while trying to film the raid as a bystander.

The longtime vendor said the Robson Square market is more about harm reduction than it is about profit, and described marijuana as a tool in the fight against an opioid overdose crisis that has killed hundreds of people in British Columbia.

"We're helping people. We're not hurting people. And that's why they don't want to go away," Woodruff said. "This isn't anarchy. This is about people who care about people."

Vancouver Coun. Melissa De Genova said she has heard mounting concerns from residents who are upset and want the city to intervene.

"They're outraged," De Genova said. "I mean, this is a public place, a public plaza. It's supposed to be family-friendly."

Bylaw officers began attempts to remove the vendors in November, starting with verbal warnings, said city spokesman Jag Sandhu. Since then, the city has issued 12 tickets, worth $1,000 each, and impounded three tents.

But De Genova said the city doesn't have enough enforcement officers to deal with all the stalls that keep popping up, adding that it is unfair for legitimate businesses who buy an operating licence and follow the rules when other vendors get away with shirking city regulations.

Charles Gauthier of the Downtown Vancouver Business Improvement Association called for the city to step in and put an end to the "illegal, open-air drug market."

Allowing pot peddlers to operate freely while at the same time requiring other outlets, such as food trucks and marijuana dispensaries, to pay licensing fees and comply with bylaws creates a double standard and leads to friction in the business community, he added.

"If I made bathtub gin and bottled it and went there and sold it on the street, I suspect that I would be shut down pretty quickly," he said.

Sgt. Jason Robillard said the police have been keeping tabs on the Robson Square stalls over the past couple of years but the department has to prioritize its resources based on public safety.

He said the situation in the public plaza has recently escalated and police have received complaints about the marijuana marketplace.

Robillard said more information would be made public later in the week.

Neil Magnuson, a marijuana vendor and director of the Cannabis Substitution Project, said the Robson Square market is a vital health service that saves lives every day.

A hundred edibles are given away at the market every day to people in need and a police crackdown is unconscionable, he said.

"We are far more here as a protest and as a harm-reduction site than a business site," Magnuson said. "The business here supports the harm reduction that we're doing."